Pteronia elongata leaves

The leaves of Pteronia elongata are simple and opposite. They grow sessile or stalkless and crowded on the upper stems.

The leaf-shape is oblong to triangular and keeled. The leaves taper to acutely pointed tips that may curve down. Their upper surfaces may be concave. The margins and keels are sparsely ciliate or fringed (or not). 

The coarse-surfaced blades are often thickish with some succulence (Bond and Goldblatt, 1984; JSTOR; iNaturalist).